The present invention relates to viscous liquids, pastes, and gels useful in various cosmetic, toiletry, cleansing and other compositions. More specifically, the present invention relates to viscous liquids, pastes, and gel compositions containing as essential ingredients alkylamido betaines, certain salts, and water.
Many cosmetic, toiletry, and cleansing compositions contain amphoteric and zwitterionic surfactants. These surfactants may serve as detergents which either replace or are in addition to anionic detergents. Betaines constitute one of the more important classes of amphoteric and zwitterionic surfactants used in such compositions. Included in the class of betaine surfactants are alkylamido betaines, alkylamino betaines, and alkyl betaines.
These compounds have the following structures: ##STR1## wherein R represents a fatty alkyl or alkenyl chain; n is an integer, usually 3.
For example, cocoamido betaine, cocoamino betaine and coco betaine are available from Lonza Incorporated, the Stepan Chemical Company, and the Miranol Chemical Co.
Sulfobetaines, wherein the carboxylate groups of the betaines described above are replaced by sulfonate groups, are also commercially available. For example, the structure of cocoamido sulfobetaine may be represented by the formula: ##STR2## wherein R and n have the same meanings as above.
Betaines are useful in a variety of compositions as a result of numerous favorable properties. In particular, they are mild, high foaming, and biodegradable surfactants and wetting agents. In addition, they are compatible with high levels of detergency builders, electrolytes, alkalis and acids. This combination of properties makes betaines useful in a variety of cleansing and industrial compositions such as alkaline and acid cleaners, light and heavy duty cleaners, metal finishing compositions, electroplating compositions, etc. The use of betaines in heavy duty cleaners, for example, is described in U.S. Pat. No. 3,876,563.
Betaines also provide good conditioning to skin and hair. As a result, betaines are frequently used in shampoo, toiletry and cosmetic compositions. The use of betaines for these applications is described in U.S. Pat. Nos. 3,328,307, 3,980,769 and 4,110,263.
As a result of the compatibility of betaines with quaternary ammonium and other germicides, betaines are also used in disinfectant and sanitizing cleansers as well as in antibacterial scrubs. Textile finishing and dye compositions are also known to benefit from the beneficial wetting, conditioning and levelling action of betaines.
It is frequently desirable for a cleaning composition to contact dome-shaped or vertical surfaces for prolonged periods of time. Freely-flowing liquids are unsuitable for this purpose since they do not remain in contact with such surfaces long enough. In order to avoid this problem, thickeners are added to the cleansing composition in order to increase viscosity and to reduce the ability of the composition to flow. Some examples of cleansing compositions which are advantageously thickened for this reason are shampoos, dishwashing detergents, toilet bowl cleaners, wall cleaners, and the like.
In addition, viscous compositions such as gels are commercially advantageous. Many consumers prefer viscous liquids and gels to non-viscous liquids because of the impression of strength conveyed as well as other aesthetic qualities. Moreover, viscous liquids and gels can be dispensed by methods other than by simple pouring. For example, viscous liquids and gels can be dispensed from tubes by squeezing.
Traditionally, the viscosity of aqueous solutions has been increased by the addition of thickening agents such as proteins,pyrogenic silicas, polyoxyethylene polymers, and natural and synthetic cellulosic gums such as hydroxypropylcellulose, methylcellulose, carboxymethylcellulose and hydroxymethylcellulose. The use of such thickening agents is disadvantageous, however, in view of the high cost and difficulty in handling involved in the use of such agents. Moreover, if a clear viscous liquid, paste or gel is desired, the use of thickening usually adds to the opaqueness of the composition.
Viscous compositions which do not require traditional thickening agents are also known. An example of such a composition is described in Murphy et al, U.S. Pat. No. 4,107,067. These compositions are said to be especially well adapted for use as detergents which are directly applied to stains and soils on fabrics during pretreatment prior to aqueous laundering. The ingredients of the Murphy et al detergent include an electrolyte and a nonionic surfactant. The electrolyte may be an alkali metal halide, sulfate, carbonate, nitrate or phosphate. The nonionic surfactant is the condensation product of a polyalkylene oxide and an aliphatic or alkyl aromatic hydrophobic compound. According to Murphy et al, the addition of an appropriate amount of electrolyte converts concentrated aqueous liquid solutions of the nonionic surfactant to gelatinous liquids and flowable gels. Gelatinous liquids are defined in this patent as those having a Brookfield viscosity in the range of about 500 cps to 10,000 cps at 72.degree. F. Flowble gels are defined as those which have Brookfield viscosities in the range of about 10,000 cps to 50,000 cps at 72.degree. F.
Lonza Incorporated has disclosed another method for forming viscous compositions in the absence of traditional thickeners. A publication giving product information on Lonzaine C, which is a solution containing cocoamido betaine and NaCl, discloses that "Lonzaine C in combination with most anionic surfactants potentiates viscosity to permit formulations ranging from viscous liquids to ringing gels". The Lonza compositions are said to be useful in a variety of cosmetic, toiletry and detergent applications.
The Murphy et al patent and the Lonza publication are unusual in that they disclose viscous aqueous compositions in the absence of additional thickening agents. The Murphy et al patent, however, is restricted to viscous detergents containing polyalkylene oxide-type nonionic surfactants. The Lonza publication is restricted to viscous compositions which require anionic surfactants in addition to cocoamido betaine.
There is a need, therefore, for viscous compositions which contain amphoteric or zwitterionic surfactants and which require neither anionic detergents nor traditional thickening agents.